Manufacturing method of airtight container, manufacturing method of image display device, and bonding method

ABSTRACT

A bonding method using a bonding agent is provided, which has the steps of forming an underlayer on a first member, providing a bonding agent on the underlayer, forming a contact member, different from the bonding agent, on a second member, bringing the bonding agent into contact with the contact member so that the first member and the second member are bonded to each other. In the method described above, the wettability of the bonding agent to the underlayer is superior to that of the bonding agent to a surface of the first member before the underlayer is formed thereon, and the bondability of the bonding agent to the contact member is superior to that of the bonding agent to a surface of the second member before the contact member is formed thereon.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods for bonding members to eachother. In addition, the present invention relates to methods formanufacturing airtight containers and image display devices.

2. Description of the Related Art

Airtight containers have been widely used. In particular, in the fieldof image display devices, manufacturing of airtight containers has beena very important technique.

At present, for image display devices, a cathode ray tube (CRT) has beenwidely used. In recent years, a CRT tube having a display screen size ofmore than 30 inches has been introduced on the market.

In addition, as a flat type image display device, for example, there maybe mentioned a plasma display device (PDP) in which a fluorescent filmis excited to emit light when irradiated with ultraviolet rays, and aflat type image display device in which a fluorescent film is excited toemit light when irradiated with electrons emitted from an electronemission element such as a field emission type (FE) electron emissionelement or a surface conduction electron emission element used as anelectron source. Recently, a PDP having a large screen size, such asapproximately 40 inches, has been available on the market.

Since the image display devices as described above each have an airtightcontainer, the manufacturing method thereof comprises a step of formingan airtight container. For example, a manufacturing method of an imagedisplay device has been known in which a substrate for an electronsource and a substrate provided with a fluorescent film are bonded toeach other to form an airtight container.

A method for bonding two members to each other, a method formanufacturing a vacuum envelope using the bonded two members, and amethod for manufacturing an image display device using the aboveenvelope are disclosed, for example, in Japanese Unexamined PatentApplication Publication No. 2002-184313. In this patent document, thestructure is disclosed in which a metal sealing material is supplied onan underlayer, and sealing is then performed.

In addition, in Japanese Patent Laid-Open No. 2002-182585, the structureis disclosed in which indium and a silicone adhesive are disposed sideby side on a frame, and sealing is then performed.

FIG. 13 is a schematic view of a general structure of a display panelformed of an electron source substrate and a large number of electronemission elements disposed thereon. In addition, FIG. 21 shows aschematic cross-sectional structure of a peripheral portion of a displaypanel (envelope 90).

In FIGS. 13 and 21, reference numeral 81 indicates an electron sourcesubstrate on which a large number of electron emission elements (notshown) are disposed, and this electron source substrate 81 may be calleda rear plate in some cases. Reference numeral 82 indicates a face platein which a fluorescent film, a metal back, and the like are formed on aglass substrate. Reference numeral 86 indicates a support frame.

The envelope 90 is formed by adhering the rear plate 81, the supportframe 86, and the face plate 82 to each other for sealing. Hereinafter,a process of sealing the envelope will be briefly described withreference to FIG. 21.

First, the rear plate 81 and the support frame 86 are bonded to eachother beforehand with a frit glass 202.

Next, an indium (In) film 93 used as a panel boding agent is providedfor the support frame 86 and the face plate 82 by soldering. In thisstep, in order to increase the adhesion of the In film 93 to the supportframe 86 and the face plate 82, silver paste films 204 are provided asan underlayer as shown in FIG. 21.

Subsequently, in a vacuum chamber, sealing is performed by bonding thesupport frame 86 to the face plate 82 with the In film 93 providedtherebetween at a temperature equal to or more than a melting point ofIn, thereby forming the envelope 90.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a novel bonding methodwhich can realize highly reliable bonding between members.

In addition, another object of the present invention is to provide amanufacturing method of an airtight container which can maintain anairtight condition with high reliability, and also to prove amanufacturing method of an image display device having superior displayperformance.

In accordance with a first aspect of the present invention, there isprovided a method for manufacturing an airtight container, whichcomprises: a bonding step of bonding a first member and a second member,in which the bonding step comprises: a first step of forming anunderlayer on the first member; a second step of providing a bondingagent on the underlayer; a third step of forming a contact member, whichis different from the bonding agent, on the second member; and a fourthstep of bringing the bonding agent into contact with the contact member.In the manufacturing method described above, the wettability of thebonding agent to the underlayer is superior to that of the bonding agentto a surface of the first member prior to the first step, thebondability of the bonding agent to the contact member is superior tothat of the bonding agent to a surface of the second member prior to thethird step, and the third step is performed after a predeterminedtreatment is performed for the second member. In the manufacturingmethod according to the first aspect of the present invention, thefirst, the second, the third, and the fourth steps described above arenot necessary to be performed in that order.

As the predetermined treatment, for example, a step of forming a film onthe second member or a step of exposing the second member to apredetermined atmosphere may be mentioned. After the predeterminedtreatment is performed, when a position of the second member on whichthe bonding agent is provided is not suitable for bonding, by performingthe third step of forming the contact member after the predeterminedtreatment, superior bonding can be realized.

According to a second aspect of the present invention, in themanufacturing method according to the first aspect, the bonding step isa step of forming a closed bond line which defines an airtight space bybonding the first member and the second member; the contact memberformed in the third step is placed at least all along a position atwhich the closed bond line is to be formed so as to be brought intocontact with the bonding agent; and the bondability of the bonding agentto the contact member placed all along the position at which the closedbond line is to be formed is superior to that of the bonding agent to asurface of the second member prior to the third step.

In accordance with a third aspect of the present invention, there isprovided a method for manufacturing an airtight container, comprising: abond line forming step of bonding a first member and a second member toform a closed bond line which defines an airtight space, in which thebond line forming step comprises: a first step of forming an underlayeron the first member; a second step of providing a bonding agent on theunderlayer; a third step of placing a contact member, which is differentfrom the bonding agent, all along a position of the second member atwhich the closed bond line is to be formed; and a fourth step ofbringing the bonding agent into contact with the contact member. In themanufacturing method described above, the wettability of the bondingagent to the underlayer is superior to that of the bonding agent to asurface of the first member prior to the first step, and the bondabilityof the bonding agent to the contact member is superior to that of thebonding agent to a surface of the second member prior to the third step.

According to a fourth aspect of the present invention, in themanufacturing method of one of the first to the third aspects, thebonding agent preferably comprises a metal. In this case, it is notalways necessary that the entire bonding agent be made of a metal. Inaddition, as a metal, an alloy may also be used. The bonding agent ispreferably has a low melting point. In particular, a bonding agenthaving a melting point of 200° C. or less is preferably used. It is morepreferable that a low melting point metal be used, and in particular,that a low melting point metal having a melting point of 200° C. or lessbe used.

According to a fifth aspect of the present invention, in themanufacturing method of one of the first to the fourth aspects, theunderlayer preferably comprises a metal. In particular, a surface of theunderlayer to be brought into contact with the bonding agent preferablycomprises a metal.

According to a sixth aspect of the present invention, in themanufacturing method of the fourth aspect, the underlayer is preferablymade of a metal which is unlikely to be oxidized as compared to that forthe bonding agent.

According to a seventh aspect of the present invention, in themanufacturing method of one of the first to the sixth aspects, thebonding agent preferably comprises an oxide at a position which is to bebrought into contact with the contact member.

According to an eighth aspect of the present invention, in themanufacturing method of one of the first to the seventh aspects, thecontact member preferably comprises an oxide at a position which is tobe brought into contact with the bonding agent.

According to a ninth aspect of the present invention, in themanufacturing method of the eighth aspect, the oxide preferablycomprises SiO₂ or PbO.

According to a tenth aspect of the present invention, in themanufacturing method of one of the first to the ninth aspects, thesecond step of providing the bonding agent on the underlayer ispreferably performed under the conditions in which at least a surface ofthe bonding agent is oxidized. For example, as the second step ofproviding the bonding agent on the underlayer, there may be a step ofdisposing the bonding agent on the underlayer at a temperature at whichat least a part of the bonding agent is melted. In addition oralternatively, a step may be used in which at least a part of thebonding agent is melted at a maximum temperature which is obtained fromthe end of the second step of providing the bonding agent to the end ofthe bonding step. In this case, the bonding agent is likely to beoxidized by oxygen present in the atmosphere. Under the conditionsdescribed above, in particular, the manufacturing method of the presentinvention is advantageously performed. In addition, at the maximumtemperature mentioned above, it is preferable that the contact member benot melted.

In accordance with an eleventh aspect of the present invention, there isprovided a method for manufacturing an image display device having anairtight container and display elements placed therein, which comprisesthe step of forming the airtight container by one of the manufacturingmethods according to the first to the tenth aspects.

According to a twelfth aspect of the present invention, in themanufacturing method of the eleventh aspect, the airtight containerpreferably comprises a first substrate, a second substrate facingthereto, and a surrounding member surrounding an airtight space formedbetween the first substrate and the second substrate, and the firstmember may be the envelope member.

According to a thirteenth aspect of the present invention, in themanufacturing method in accordance with the eleventh aspect, theairtight container preferably comprises a first substrate, a secondsubstrate facing thereto, and a surrounding member surrounding anairtight space formed between the first substrate and the secondsubstrate, and the first member may be the first substrate or the secondsubstrate.

In accordance with a fourteenth aspect of the present invention, thereis provided a method for manufacturing an image display device having anairtight container and display elements placed therein, comprising thestep of forming the airtight container by the manufacturing methodaccording to the first aspect or the second aspect. In the method formanufacturing an image display device, described above, thepredetermined treatment is a step of forming at least a part of thedisplay elements on the second member or a step of forming at least apart of wires, which supply signals to the display elements, on thesecond member. This manufacturing method in accordance with thefourteenth aspect may also be combined with at least one of the methodsin accordance with the fourth to the tenth aspects.

In accordance with a fifteenth aspect of the present invention, there isprovided a method for manufacturing an image display device having anairtight container and display elements placed therein, comprising thestep of forming the airtight container by the manufacturing methodaccording to the first aspect or the second aspect. In the method formanufacturing an image display device, described above, thepredetermined treatment is a step of forming at least a part of wires,which supply signals to the display elements, on the second member, andat least a part of the contact member is formed on said at least a partof wires. This manufacturing method in accordance with the fifteenthaspect may also be combined with at least one of the methods inaccordance with the fourth to the tenth aspects.

In accordance with a sixteenth aspect of the present invention, there isprovided a method for manufacturing an image display device having anairtight container and display elements placed therein, comprising thestep of forming the airtight container by the manufacturing methodaccording to the first aspect or the second aspect of the presentinvention. In the method for manufacturing an image display device,described above, the predetermined treatment is a step of forming anelectrode or a fluorescent film on the second member. This manufacturingmethod in accordance with the sixteenth aspect may also be combined withat least one of the methods in accordance with the fourth to the tenthaspects. In addition, each of the methods for manufacturing an imagedisplay device, described above, may further comprise a step of formingthe display elements described above. The step of forming the displayelements may be performed before or after the step of forming theairtight container. In addition, when the step of forming the displayelements includes a plurality of substeps, some of the substeps may beperformed before the step of forming the airtight container and theother substeps may be performed after the step described above.

In accordance with a seventeen aspect of the present invention, there isprovided a bonding method using a bonding agent, comprising the stepsof: forming an underlayer on a first member; providing the bonding agenton the underlayer; forming a contact member, which is different from thebonding agent, on a second member; and bringing the bonding agent intocontact with the contact member so that the first member and the secondmember are bonded to each other. In the bonding method described above,the wettability of the bonding agent to the underlayer is superior tothat of the bonding agent to a surface of the first member before theunderlayer is formed thereon, and the bondability of the bonding agentto the contact member is superior to that of the bonding agent to asurface of the second member before the contact member is formedthereon.

According to the aspects of the present invention described above, it ispreferable when the bondability of the contact member to the bondingagent is superior to that of the same material as that for theunderlayer, which is provided on the second member instead of thecontact member, to the bonding agent.

In the manufacturing methods in accordance with the aspects of thepresent invention, described above, the step of bringing the bondingagent into contact with the contact member is preferably performed in areduced-pressure atmosphere.

In the manufacturing methods in accordance with the aspects of thepresent invention, the temperature at which the bonding agent and thecontact member are brought into contact with each other is preferably atemperature at which the contact member will not flow. In particular,before the bonding agent and the contact member are brought into contactwith each other, and in more particular, after the bonding agent isprovided on the underlayer and before the bonding agent and the contactmember are brought into contact with each other, the temperature may beincreased so that the bonding agent has a high fluidity; however, in thecase described above, the bonding agent and the contact member arepreferably brought into contact with each other when the fluidity of thebonding agent is suppressed by decreasing the temperature lower thanthat at which the high fluidity of the bonding agent is obtained. Inaddition, in the manufacturing methods of the present inventiondescribed above, as the underlayer, silver, gold, platinum, or an alloycontaining at least one of the metals mentioned above is preferablyused.

Further objects, features and advantages of the present invention willbecome apparent from the following description of the preferredembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a peripheral portion of anenvelope of the present invention.

FIG. 2 is a schematic plan view of the structure of an electron sourceused for an image display device of the present invention.

FIG. 3 is an explanatory view of a manufacturing step of the electronsource shown in FIG. 2.

FIG. 4 is an explanatory view of a manufacturing step of the electronsource shown in FIG. 2.

FIG. 5 is an explanatory view of a manufacturing step of the electronsource shown in FIG. 2.

FIG. 6 is an explanatory view of a manufacturing step of the electronsource shown in FIG. 2.

FIG. 7 is an explanatory view of a manufacturing step of the electronsource shown in FIG. 2.

FIGS. 8A, 8B, and 8C are explanatory views of a manufacturing step ofthe electron source shown in FIG. 2.

FIGS. 9A and 9B are graphs of a foaming voltage with time.

FIG. 10 is a schematic view of an apparatus for measuring properties ofan electron emission element of the present invention.

FIG. 11 is a graph showing the relationship of an element voltage withan element current and an emission current of a surface conduction typeelectron emission element of the present invention.

FIGS. 12A and 12B are graphs of an activation voltage with time.

FIG. 13 is a schematic perspective view of a general structure of animage display device.

FIGS. 14A and 14B are schematic perspective views of a fluorescent filmof an image display device of the present invention.

FIG. 15 shows a drive circuit of an image display device of the presentinvention.

FIG. 16 is an explanatory view of a forming method of an In film(bonding agent) of the present invention.

FIG. 17 is a schematic view of the structure used for a sealing methodof the present invention.

FIG. 18 is a schematic cross-sectional view of the structure of aperipheral portion of an envelope according to the present invention.

FIG. 19 is a schematic view of the structure used for a sealing methodof the present invention.

FIG. 20 is a schematic view of one example of the structure of a surfaceconduction type electron emission element.

FIG. 21 is a schematic cross-sectional view of one example of thestructure of a peripheral portion of a related envelope.

FIG. 22 is a schematic view of one example of a related sealing method.

FIG. 23 is a side view showing of the structure of a peripheral portionof an envelope according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments according to the above invention will be described. Inthe embodiments, a bonding method and a manufacturing method of an imagedisplay device, which is also a manufacturing method of an airtightcontainer, according to the present invention, will be described withreference to particular examples. In particular, it is intended torealize the embodiment in which a bonding agent is provided so as toexhibit superior and uniform properties. When an underlayer to improvethe wettability is formed on one of members, that is, a first member,the uniformity can be improved. As a process in which a bonding agent isprovided using the wettability, a process may be preferably used inwhich at least a part of the bonding agent is melted while being incontact with the underlayer. In more particular, the process describedabove can be achieved when a bonding agent in a molten state is providedon an underlayer, or when a boding agent is melted after disposedthereon. When a uniform bonding agent is realized using the wettability,it was found that the presence of an oxide formed on the surface of thebonding agent may cause a problem. For example, when a bonding agent isprovided on an underlayer while being heated, or when a bonding agent isprovided thereon in an oxygen-containing atmosphere, such as in the air,the surface of the bonding agent is liable to be oxidized. Accordingly,a contact member having superior bondability to the other member, thatis, a second member to be bonded to the first member mentioned above, isprovided on the second member, thereby improving the bondability betweenthe first and the second members.

The difference in wettability in the present invention can be confirmedby the following method. That is, the spread width of the bonding agentapplied on the underlayer of the first member is measured. Next, thespread width of the bonding agent applied on the first member, which isnot provided with the underlayer (prior to the formation of theunderlayer), under the same condition as that in the above measurementis measured. Subsequently, the spread width obtained when the underlayeris provided is divided by that obtained when the underlayer is notprovided, and when the value thus obtained is one or more, it isconfirmed that the wettability of the bonding agent to the underlayer issuperior to that of the bonding agent to a surface of the first memberwhich is not provided with the underlayer.

In addition, the bondability of the bonding agent to the contact membersuperior to that of the bonding agent to a surface of the second member,which is not provided with the contact member (prior to the formation ofthe contact member), can be confirmed by the following method. That is,a first airtight container is formed using the bonding method or themanufacturing method of an airtight container, according to the presentinvention. An air pipe is provided for this airtight container. Tenfirst airtight containers are formed. Under the same conditions as thosefor this first airtight container, a second airtight container is formedusing the second member which is not provided with the contact member.An air pipe is also provided for the second airtight container. Tensecond airtight containers are also formed. To these airtightcontainers, helium is blown, and using a helium leak detector connectedto the air pipe provided for each airtight container, the amount ofhelium which enters the airtight container is measured. The measurementcondition is set such that a helium amount of 1×10⁻¹² Pa·m³/s or more isdetected for at least five out of the 20 airtight containers. Inparticular, first, the helium amounts of the airtight containers aremeasured while a force is not applied to the bonded portion in aseparating direction. In this step, when a helium amount of 1×10⁻¹²Pa·m³/s or more is detected for four airtight containers or less out ofthe 20 airtight containers, after a force is slightly applied to thebonded portion thereof in a separating direction, the helium amount isthen measured for the 20 airtight containers. When the total number ofthe airtight containers is less than five which have a helium amount of1×10⁻¹² Pa·m³/s or more, after an increased force is further applied tothe bonded portion in a separating direction, the helium amount of the20 airtight containers are then measured. After a series of measurementsin which a predetermined separating force is applied (or a first set ofmeasurements in which a separating force is not applied), when thenumber of airtight containers which have a helium amount of 1×10⁻²Pa·m³/s or more is five or more, the measurement is stopped. Airtightcontainers which have helium amount of less than 1×10⁻¹² Pa·m³/s areregarded as a good product, and good product rates of the two typecontainers are then compared to each other. When the good product rateof the first airtight containers is higher than that of the secondairtight containers, then it is confirmed that the bondability of thebonding agent to the contact member is superior to that of the bondingagent to a surface of the second member which is not provided with thecontact member.

Hereinafter, with reference to drawings, preferred embodiments of thepresent invention will be describe by way of example. However, it is tobe understood that the dimensions, materials, arrangement, and the likeof constituent elements described in these embodiments will not limitthe present invention at all. In the embodiments, an electron emissionelement is used as a display element; however, as a display element,other elements such as an electroluminescent element and a plasmadisplay element may also be used.

In an image display device of this embodiment, as an electron emissionelement disposed at an electron source, an element having the structureshown in FIG. 20 is used.

A substrate 21 is made of glass or the like, and the size and thethickness thereof are appropriately determined, for example, inconsideration of the number of electron emission elements and designedshapes of the individual elements. In addition, when the substrate isformed to serve as a part of a container while an electron source isoperated, dynamic conditions, such as a structure having resistanceagainst an atmospheric pressure so that the container is held undervacuum, are also taken into consideration.

As a glass material, an inexpensive blue sheet glass may be used. Inaddition, on the glass substrate, a silicon oxide film is preferablyformed thereon to form a two-layered substrate. When a blue sheet glassis used as the substrate, in particular, this silicon oxide film may beused as a sodium blocking layer. The silicon oxide film is preferablyformed to have a thickness of approximately 0.5 μm. In addition, thissilicon oxide film is preferably formed by sputtering. Furthermore, aglass containing a small amount of sodium and a quartz substrate mayalso be used as the substrate of the embodiments according to thepresent invention.

As a material for element electrodes 22 and 23, a common conductivematerial is used, and a metal or an alloy, such as nickel (Ni), chromium(Cr), gold (Au), molybdenum (Mo), platinum (Pt), titanium (Ti) or apalladium (Pd)-silver (Ag) alloy, may be preferably used. In addition, aprinted conductive material formed of a metal oxide, a glass and thelike, a transparent conductor such as indium tin oxide (ITO), or thelike may also be used. The thickness thereof is preferably in the rangeof from several hundreds of angstroms to several micrometers.

A distance L between the element electrodes, a length W, the shape, andthe like thereof are appropriately designed in accordance withapplication in which the element is practically used; however, thedistance L is preferably in the range of from several thousands ofangstroms to one millimeter, and more preferably, in consideration of avoltage applied between the element electrodes, in the range of from 1to 100 μm. In addition, the length W is preferably in the range of fromseveral to several hundreds of micrometers in consideration of theelectrode resistance and electron emission properties.

A conductive film (element film) 27 used as an electron source is formedso as to be placed on both element electrodes 22 and 23.

As the conductive film 27, in order to obtain superior electron emissionproperties, a fine particle film made of fine particles is particularlypreferable. In addition, the thickness thereof is optionally set, forexample, in consideration of a step coverage for the element electrodes22 and 23, the resistance therebetween, and foaming treatment conditionswhich will be described later; however, the thickness is preferably inthe range of from several to several thousands of angstroms, and morepreferably, in the range of from 10 to 500 Å. The sheet resistancethereof is preferably in the range of from 10³ to 10⁷ Ω.

As a material for the conductive film, in general, Pd is suitably used;however, the material is not limited thereto. In addition, as afilm-forming method, for example, sputtering or firing performed afterapplication of solution may be optionally used.

An electron emission portion 28 is formed, for example, by supplyingelectricity as described below. For the convenience of illustration inthe figures, the electron emission portion 28 in a rectangular shape isshown at the center of the conductive film 27; however, this is aschematic view, and the position and the shape of an actual electronemission portion are not precisely shown in the figure.

When electricity is supplied between the element electrodes 22 and 23 bya power source not shown in the figure at a predetermined vacuum level,the structure of a part of the conductive film 27 is changed to form agap (crack), and this gap area forms the electron emission portion 28.In addition, electron emission occurs in the vicinity of the gap formedby this foaming at a predetermined voltage; however, the efficiency ofelectron emission in this state is very low.

Examples of voltage waveforms used in foaming (hereinafter referred toas “electrical foaming”) by electricity supply are shown in FIG. 9. Inparticular, the voltage waveform is preferably a pulse waveform. As amethod therefor, for example, there may be mentioned a method in which apulse having a constant peak pulse voltage is sequentially applied asshown in FIG. 9A and a method in which a pulses is applied while thepeal pulse voltage is increased as shown in FIG. 9B.

First, the case in which the peak pulse voltage is constant will bedescribed with reference to FIG. 9A. In FIG. 9A, T1 and T2 indicate apulse width and a pulse interval, respectively. In general, T1 is set inthe range of from 1 μs to 10 ms, and T2 is set in the range of from 10μs to 100 ms. The peak voltage (peak voltage in electrical foaming) of atriangle waveform is appropriately selected in accordance with the stateof the electron emission element. Under the conditions described above,for example, a voltage is applied for several seconds to several tens ofminutes. The pulse wave is not limited to a triangle wave. A desiredwaveform such as a rectangular waveform may also be used.

Next, the case in which a pulse is applied while the peak pulse voltageis increased will be described with reference to FIG. 9B. T1 and T2 inFIG. 9A may be the same as those shown in FIG. 9A. The peak voltage(peak voltage in electrical foaming) of a triangle waveform may beincreased, for example, by approximately 0.1 V per step.

The electrical foaming may be stopped when the resistance reaches, forexample, 1 MΩ or more which is obtained by measuring current flowingthrough an element to which a pulse voltage is applied.

After this electrical foaming is completed, the electron emissionefficiency is very low. Accordingly, in order to increase the electronemission efficiency, treatment called “activation” is preferablyperformed for the element.

This activation treatment can be performed when a pulse voltage isrepeatedly applied between the element electrodes 22 and 23 in anappropriate vacuum atmosphere in which an organic compound is present.By introducing a gas containing carbon atoms, carbon or a carboncompound derived therefrom is deposited in the vicinity of the gap(crack) as a carbon film.

In one example of this process, trinitrile to be used as a carbon sourceis introduced in a vacuum space through a slow leak valve, and theinside is maintained at a pressure of approximately 1.3×10⁻⁴ Pa.Although being slightly influenced, for example, by the shape of avacuum device and members provided therein, the pressure of thetrinitrile thus introduced is preferably set in the range of fromapproximately 1×10⁻⁵ to 1×10⁻² Pa.

In FIGS. 12A and 12B, preferable examples of voltage application used inthe activation step are shown. A maximum applied voltage is optionallyselected from the range of 10 to 20 volts.

In FIG. 12A, T1 indicates a pulse width of each of a positive and anegative voltage waveform, T2 indicates a pulse interval, and theabsolute values of the positive and the negative voltages are set equalto each other. In addition, in FIG. 12B, T1 and T1′ indicate pulsewidths of a positive and a negative voltage waveform, respectively, T2indicates a pulse interval, T1>T2 is satisfied, and the absolute valuesof the positive and the negative voltages are set equal to each other.

In the case described above, when an emission current Ie reaches anapproximately saturated level, the supply of electricity is stopped, andthe slow leak valve is closed, thereby stopping the activationtreatment.

By the steps described above, an electron emission element as shown inFIG. 20 can be formed.

Basic properties of an electron emission element, which has the elementstructure and is formed by the manufacturing method as described above,will be described with reference to FIGS. 10 and 11.

FIG. 10 is a schematic view of a measurement apparatus for measuringelectron emission properties of an electron emission element having thestructure described above. In FIG. 10, reference numeral 51 indicates apower source applying an element voltage Vf to an element; referencenumeral 50 indicates an ampere meter measuring an element current Ifflowing through an electrode portion of the element; reference numeral54 is an anode collecting an emission current Ie emitted from anelectron emission portion of the element; reference numeral 53 indicatesan high voltage power source applying a voltage to the anode 54; andreference numeral 52 is an ampere meter measuring the emission currentIe emitted from the electron emission portion.

When the element current If flowing between the element electrodes 22and 23 of the electron emission element and the emission current Ieflowing to the anode are measured, the power source 51 and the amperemeter 50 are connected to the element electrodes 22 and 23, and theanode 54 connected to the power source 53 and the ampere meter 52 isdisposed above the electron emission element.

In addition, the electron emission element and the anode 54 are placedin a vacuum device 55, and a vacuum pump 56 and necessary components,such as a vacuum meter, required for a vacuum device are provided forthe vacuum device 55, so that the measurement of the electron emissionelement can be performed at a desired vacuum level. In addition, themeasurement is performed at a voltage of the anode 54 of 1 to 10 kV andat a distance H between the anode and the electron emission element of 2to 8 mm.

A typical example of the relationship of the element voltage Vf with theemission current Ie and the element current If measured by themeasurement device shown in FIG. 10 is shown in FIG. 11. In this graph,although the magnitude of the emission current Ie is appreciablydifferent from that of the element current If, since the changes of Ifand Ie are qualitatively compared to each other, the vertical axis ofthis graph represents a linear arbitrary unit.

This electron emission element has three features on the emissioncurrent Ie.

First, as can be seen in FIG. 11, when an element voltage having acertain level (hereinafter referred to as “threshold voltage”, Vth shownin FIG. 11) or more is applied to this element, the emission current Ieis rapidly increased, and on the other hand, when an element voltage isless than the threshold voltage Vth, the emission current Ie is notsubstantially sensed. That is, it is understood that this element hasproperties as a nonlinear element which has an apparent thresholdvoltage Vth with respect to the emission current Ie.

Secondary, since depending on the element voltage Vf, the emissioncurrent Ie can be controlled by the element voltage Vf.

Thirdly, the amount of emission charge collected by the anode 54 dependson the time for applying the element voltage Vf. That is, the amount ofcharge collected by the anode 54 can be controlled by the time forapplying the element voltage Vf.

Next, an electron source and an image display device of this embodimentwill be described.

As a basic structure of this embodiment, for example, the structureshown in FIG. 2 may be mentioned. In this electron source, on asubstrate 81, there are provided a plurality of Y-direction wires (lowerwires) 24 and a plurality of X-direction wires (upper wires) 26 abovethe Y-direction wires 24 with an insulating layer 25 providedtherebetween, and in the vicinity of each of the intersecting positionsbetween the two direction wires, an electron emission element containinga pair of electrodes (element electrodes 22 and 23) is provided.

The image display device of this embodiment has the structure having anelectron source as shown in FIG. 2, and a basic structure thereof willbe described with reference to FIG. 13 which shows a general structureof an image display device.

In FIG. 13, reference numeral 81 indicates a substrate forming theelectron source, reference numeral 82 indicates a face plate, which is asubstrate formed of a fluorescent film 84, a metal back 85, and the likeprovided on a glass plate 83, and reference numeral 86 indicates asupport frame used as a surrounding member. The substrate 81 forming theelectron source, the support frame 86, and the face plate 82 are bondedto each other with a bonding agent such as an In film or a frit glass,followed by firing at 400 to 500° C. for 10 minutes or more for sealing,thereby forming an envelope 90 used as an airtight container.

When a support body called a spacer (not shown in the figure) isdisposed between the face plate 82 and the electron source substrate 81,an envelope 90 having a sufficient strength against an atmosphericpressure can be formed which may be used for a large area panel.

A method for manufacturing an envelope of this embodiment comprises thesteps of bonding the support frame 86 first to the electron sourcesubstrate 81 or the face plate 82 with a frit glass or the like, formingan underlayer on a contact face of the support frame 86 when theenvelope 90 is formed with a predetermined space between the electronsource substrate 81 and the face plate 82, and then providing a bondingagent on this underlayer. In the step described above, the underlayer isselected so that the wettability of the bonding agent to the underlayeris superior to that of the bonding agent to a surface of the supportframe 86 which is not provided with the underlayer.

As the bonding agent, a metal is preferably used, and in particular alow melting point metal is preferably used. A bonding agent having amelting point of 200° C. or less is preferably used. In addition, when ametal is used as the bonding agent, indium or an alloy thereof may bepreferably used as the metal.

In addition, for the underlayer, a metal is preferably used, and inparticular a metal unlikely to be oxidized is preferably used. Theunderlayer preferably has a composition different from that of thebonding agent. In particular, when a metal is used for the bondingagent, a metal which is unlikely to be oxidized as compared to that forthe bonding agent is preferably used for the underlayer. The degree ofresistance against oxidation is defined by the value of the standardredox potential. For this underlayer, silver, gold, platinum, or analloy containing at least one of metals mentioned above is preferablyused.

In addition, on a position of the other substrate (substrate to whichthe support frame 86 is not bonded), which opposes the bonding agent, acontact member having a composition different from that of the bondingagent is provided. In this step, the bondability of the bonding agent tothe contact member is superior to that of the bonding agent to a surfaceof the other substrate (substrate to which the support frame 86 is notbonded) which is not provided with the contact member.

As the contact member, an oxide film is preferably used, and inparticular, SiO₂ or PbO is preferable.

In addition, the materials or the shapes of the underlayer and thecontact member or both the materials and the shapes thereof arepreferably different from each other. Although the same material may beused for the underlayer and the contact member, superior wettability andbondability may not be always obtained at the same time. In particular,when the surface of the bonding agent has an oxide layer, it becomesdifficult to obtain those properties at the same time. In thisembodiment, even when a surface (surface before the contact member isformed thereon) on which the contact member is to be formed comprises anoxide, an oxide film is formed as the contact member. For example, whena member on which the contact member is to be formed is a substrateforming the electron source, although the substrate forming the electronsource has an oxide layer on the surface thereof, for example, aposition of the substrate, which is to be brought into contact with thebonding agent, may be contaminated by treatment such as the formation ofelectron emission elements or the formation of wires and/or may beprovided with members such as wires or the like. In addition, when amember on which the contact member is to be formed is a substrateforming the face plate, although the substrate forming the face platehas an oxide layer on the surface thereof, for example, a position ofthe substrate, which is to be brought into contact with the bondingagent, may be contaminated by treatment such as the formation of thefluorescent film or the formation of the metal back used as anaccelerating electrode and/or may be provided with members such as theelectrode, wires, and the like. Accordingly, the step of forming thecontact member on a member is preferably performed after at least onetreatment is finished which should be carried out for the member beforethe step of bringing the contact member into contact with the bondingagent. In particular, the step of forming the contact member on a memberis preferably performed after the formation of predetermined constituentelements such as wires and/or electrodes is performed on a position ofthe member which is brought into contact with the bonding agent. Moreparticularly, the step of forming the contact member on a member is mostpreferably performed after all the treatment is finished which should becarried out for the member before the step of bringing the contactmember into contact with the bonding agent.

In addition, a bonded portion made by the underlayer, the bonding agent,and the contact member is formed as a closed bond line along the supportframe functioning as the surrounding member. For example, in thestructure shown in FIG. 13, when wires are formed on the surface of thesubstrate 81 forming the electron source so as to extend outside pastthe bond line, and when the substrate 81 forming the electron source isthe substrate on which the contact member is formed, even if thesubstrate 81 has an oxide on the surface thereof as is a substrate whichis coated with a silicon oxide film, since the wires are formed thesurface, the bondability at the positions on which the wires are formedmay be insufficient in some cases. In the case described above, thecontact member may be formed at least on the positions at which thewires are formed. That is, after the contact member having superiorbondability to the bonding agent is placed all along the position atwhich the bond line is to be formed so as to be brought into contactwith the bonding agent, the contact member may then be brought intocontact with the bonding agent. More preferably, after the step offorming the contact member all along the position at which the bond lineis to be formed, the contact member is then brought into contact withthe bonding agent. In addition, the underlayer is also preferably formedall along the position at which the bond line is to be formed.

The bonding method of the present invention is preferably used inparticular when the bonding is performed in a reduced-pressureatmosphere, and in more particular, and the bonding method is suitablyused when the step of providing the bonding agent on the underlayer isperformed in an atmosphere in which at least the surface of the bondingagent is oxidized.

In addition, in the step of providing the bonding agent on theunderlayer, when the bonding agent is melted and disposed, the bondingmethod of the present invention is preferably used.

Particular structure, operation, and the like of a vacuum sealed portionof the image display device of this embodiment will be described indetail with reference to the examples described later.

The internal pressure (total pressure) of an envelope, that is, anairtight container, of this example was 10⁻⁵ Pa or less. After thispressure was obtained, getter treatment was also performed in order tomaintain the vacuum level in the envelope 90 after sealing.

Of the getters, there are an evaporation and a non-evaporation typegetter. An evaporation type getter, made of an alloy primarilycontaining Ba or the like, is heated in the envelope 90 by applyingelectricity or high frequency to form a deposition film (getterflashing) on the inside wall of the container, and hence gases generatedinside are absorbed by an active getter metal surface, therebymaintaining high vacuum.

On the other hand, as for a non-evaporation type getter, a gettermaterial made of Ti, Zr, V, Al, Fe, or the like is disposed and heatedin a vacuum state for “getter activation” in order to obtain gasabsorption properties, thereby absorbing generated gases.

In general, since a flat type image display device has a smallthickness, it is difficult to secure a region in which an evaporationtype getter is disposed and a flash region for instantaneous discharge,and hence the getter is provided in the vicinity of a support framewhich is located outside an image display area. Accordingly, theconductance between the central portion of the image display and theregion at which the getter is provided is decreased, and as a result,the effective evacuation rate at the central portion of the electronemission elements and/or the fluorescent film is decreased.

In the image display device having an electron source and an imagedisplay member, an area at which unfavorable gases are generated is theimage display region which is irradiated primarily with electron beams.Hence, in order to maintain the fluorescent film and the electron sourceat a high vacuum level, non-evaporation type getters are preferablydisposed in the vicinity of the fluorescent film and the electronsource, which evolve gases.

The structure of an image display device for television display based ontelevision signals of an NTSC system is shown in FIG. 15 by way ofexample which uses a display panel formed of a simple matrix typeelectron source as shown in FIG. 2.

In FIG. 15, reference numeral 101 indicates an image display panel(envelope) as shown in FIG. 13, reference numeral 102 indicates ascanning circuit, reference numeral 103 indicates a control circuit,reference numeral 104 indicates a shift register, reference numeral 105indicates a line memory, reference numeral 106 indicates asynchronization signal separation circuit, reference numeral 107indicates an information signal generator, and symbol Va indicates a DCpower source.

As described above, in the image display device of the presentinvention, electron emission is performed by applying a voltage to eachelectron emission element through two types of direction wires, andelectron beams thus generated are accelerated by applying a high voltageto the metal back 85 used as an anode through a high voltage terminal Hvconnected to the DC power source Va so as to collide with thefluorescent film 84, thereby displaying an image.

In this case, according to the manufacturing method of the image displaydevice of this embodiment, the generation of vacuum leak at a weldedportion can be significantly effectively suppressed, and an image havingsuperior quality can be displayed for a long period of time.

The structure of the image display device described in this embodimentis one example of the image display devices of the present invention,and various modification may be made in accordance with the spirit andthe scope of the present invention. As for input signals, an NTSC systemis described by way of example; however input signals are not limitedthereto, and PAL, HDTV, or the like may also be used.

EXAMPLES

Hereinafter, examples of the present invention will be described;however, the present invention is not limited to the following examples.

Example 1

In this example, an electron source was formed which was composed of agreat number of surface-conduction electron emission elements wired in amatrix as shown in FIG. 2, and by using this electron source, an imagedisplay device as shown in FIG. 13 was formed.

First, on the electron source substrate 81, as the electron emissionelements electron emission elements shown in FIG. 20 were formed.

Hereinafter, a manufacturing method of the electron source, according tothis example, will be described with reference to FIGS. 2 to 8.

(Formation of Element Electrode)

On the glass substrate 81, after titanium (Ti) 5 nm thick was firstdeposited by sputtering as an underlying layer, a platinum (Pt) film 40nm thick was formed thereon, and subsequently, patterning was performedby a photolithographic method including application of a photoresist,exposure, development, and etching, thereby forming element electrodes22 and 23 (see FIG. 3). In this example, the distance L between theelement electrodes was set to 10 μm, and the length W of one electrodefacing to the other electrode was set to 100 μm.

(Formation of Y-Direction Wires)

Wire materials for Y-direction wire 24 and X-direction wire 26 arepreferably a low-resistance material which can supply an approximatelyuniform voltage to a great number of surface-conduction electronemission elements, and in addition to the wire material, the thickness,width, and the like of the wires may be appropriately determined.

The Y-direction wires 24 were formed by the steps of screen-printing asilver (Ag) paste ink, drying the ink thus printed, and then firing theink at a temperature of approximately 420° C. (see FIG. 4). TheY-direction wires 24 were each connected to element electrodes disposedin the Y direction, each of which is one type of the pair of elementelectrodes, and were formed so as to function as a scanning electrodeafter a panel was formed. The thickness of this Y-direction wire 24 wasapproximately 15 μm, and the width thereof was approximately 100 μm. Inaddition, lead wires connected to an external drive circuit were formedby the method similar to that described above.

(Formation of Interlayer Insulating Layers)

In order to insulate between the X-direction and the Y-direction wires,interlayer insulating layers 25 were formed. In order to cover theintersections between the X-direction wires which are described laterand the Y-direction wires (scanning signal wires) which were formedbeforehand, and in order to obtain electrical connection between theX-direction wire and the element electrodes, each of which is the othertype of the pair of element electrodes, the interlayer insulating layers25 were each formed to have contact holes at connection portionscorresponding to the individual elements (see FIG. 5).

In particular, after a photo-glass paste was screen-printed over theentire surface, exposure using a photomask having a predeterminedpattern was performed, followed by development, and finally firing wasperformed. In this example, a process including printing, exposure,development, and firing was repeated four times, thereby forming alaminate. The firing was performed at a temperature of approximately480° C. The thickness of this interlayer insulating layer 25 wasapproximately 30 μm on the whole, and the width thereof was 150 μm.

(Formation of X-direction Wires)

The X-direction wires 26 used as a common wire were each connected tothe other type of the pair of electrodes, which was disposed in the Xdirection, and were formed in a stripe pattern (see FIG. 6). After asilver (Ag) photo-paste ink used as a material was screen-printed,followed by drying, exposure was performed using a photomask having apredetermined pattern, and then development was performed. Subsequently,the wires were formed by firing at a temperature of approximately 480°C. The thickness of this X-direction wire 26 was approximately 10 μm,and the width thereof was approximately 50 μm.

As described above, a substrate having an XY matrix wire arrangement wasformed.

(Formation of Conductive Film)

Next, after the substrate was sufficiently washed, the surface thereofwas processed with a solution containing water-repellent agent so as toform a hydrophobic surface. The reason for this is that an aqueoussolution for forming a conductive film, which is subsequently applied onthe surface of the substrate, is disposed so as to be appropriatelyspread over the element electrodes.

Subsequently, the conductive film 27 was formed between the elementelectrodes 22 and 23. This step will be described with reference toschematic views shown in FIGS. 8A to 8C. In order to compensate for atwo-dimensional positional deviation of each element electrode on thesubstrate 81, after the positional deviations of the pattern weremeasured at several points on the substrate, the amounts of deviationbetween the measurement points were linearly approximated, followed byperforming positional correction, and a conductive-film forming materialwas then applied. Accordingly, the positional deviation for each pixelcould be corrected, and application of the material could be preciselyperformed onto the appropriate positions.

In this example, in order to obtain a palladium film as the conductivefilm 27, a palladium-proline complex was dissolved to have aconcentration of 0.15 percent by weight in an aqueous solutioncontaining water and isopropyl alcohol (IPA) at a ratio of 85 to 15,thereby forming an a solution containing organic palladium. To thissolution, a small amount of additives was added. Droplets of thissolution were applied between the element electrodes using an inkjetejecting device provided with a piezoelectric element as adroplet-applying device so as to obtain a dot diameter of 60 μm (FIG.8A).

Subsequently, this substrate was processed by firing performed at 350°C. for 10 minutes in the air, thereby forming a conductive film 27′ madeof palladium oxide (PdO) (FIG. 8B). A film having a dot diameter ofapproximately 60 μm and a maximum thickness of 10 nm was obtained.

(Foaming Step)

Next, in the step called a foaming step, a crack was formed inside theconductive film 27′ by applying electricity, thereby forming theelectron emission portion 28 (FIG. 8C).

As a particular method, a vacuum space was formed between the substrate81 and a hood-shaped lid, which was provided so as to cover the entiresubstrate except for lead wire portions disposed along the periphery ofthe substrate 81, and a voltage was then applied between the twodirection wires 24 and 26 through terminals of these lead wires by anexternal power source so that electricity was applied between theelement electrodes 22 and 23. Accordingly, a part of the conductive film27′ was damaged, deformed, or modified, and as a result, the electronemission portion 28 having a high electrical resistance was formed.

In this step, when the application of electricity was performed duringheating in a vacuum atmosphere containing a small amount of a hydrogengas, reduction was facilitated by the presence of hydrogen, and as aresult, the conductive film 27′ made of palladium oxide (PdO) waschanged into the conductive film 27 made of palladium (Pd).

In this change caused by the reduction, the contraction of the filmoccurred, and a crack was generated in a part thereof; however, theposition at which the crack was generated and the shape thereof werelargely depend on the uniformity of the original film. In order tosuppress the variation in properties among a great number of elements,the crack was preferably generated at the central portion of theconductive film 27 and most preferably had a linear shape.

From the vicinity of the crack formed by this foaming, electron emissionalso occurred at a predetermined voltage; however, the emissionefficiency was still very low under the current conditions.

The foaming treatment in this example was performed using a pulsewaveform as shown in FIG. 9B, and T1 and T2 were set to 0.1 ms and 50ms, respectively. An applied voltage was set to 0.1 V at the start andwas then increased stepwise every five seconds by approximately 0.1 V.In order to stop the electrical foaming, a current flowing through theelement during application or a pulse voltage was measured to obtain theresistance, and when this resistance became 1,000 times or more theresistance obtained before the foaming treatment, the foaming treatmentwas stopped.

(Activation Step)

As was the foaming described above, a vacuum space was formed betweenthe substrate 81 and a hood-shaped lid provided thereon for covering,and a pulse voltage was repeatedly applied between the elementelectrodes 22 and 23 from the outside through the two direction wires 24and 26. In addition, a gas containing carbon atoms was introduced in thespace, so that carbon or a carbon compound derived therefrom wasdeposited as a carbon film in the vicinity of the crack.

In this example, trinitrile was used as a carbon source and wasintroduced into the vacuum space through a slow leak valve, and thepressure was maintained at 1.3×10⁻⁴ Pa.

FIG. 12 shows an example of a preferable voltage application used in theactivation step. The maximum voltage for application was appropriatelyselected from the range of from 10 to 20 V.

After approximately 60 minutes from the start, at which the emissioncurrent Ie was approximately saturated, the application of electricitywas stopped, and the slow leak valve was closed, thereby finishing theactivation treatment.

By the steps described above, an electron source composed of a greatnumber of electron emission elements wired in a matrix on the board wasformed.

Next, by using the electron source thus formed, an image display devicewas then manufactured. With reference to FIGS. 1, 13, and 14, themanufacturing method will be described.

FIG. 1 is a schematic cross-sectional view of the peripheral portion ofthe envelope 90 of the image display device according to this example.

In FIG. 1, reference numeral 81 indicates the substrate of the electronsource provided with a great number of electron emission elements, andthis substrate is called a rear plate. Reference numeral 82 indicatesthe face plate composed of a glass substrate, a fluorescent film, and ametal back, the latter two constituent elements being provided on theinternal surface of the glass substrate.

FIGS. 14A and 14B are explanatory views of the fluorescent film 84provided on the face plate 82. The fluorescent film 84 is composed ofonly a fluorescent material in the case of monochrome display, and inthe case of a fluorescent film for color display, the color fluorescentfilm is formed of fluorescent units 92 and a black conductor 91, whichis called a black stripe or black matrix depending on the arrangement ofthe fluorescent units. An object of the black stripe or the black matrixthus provided is to darken areas located between the individualfluorescent units, such as three primary color fluorescent unitsrequired for color display, so as to hide unfavorable color mixture orthe like, in addition, is to suppress the decrease in contrast at thefluorescent film 84 caused by external light reflection.

In addition, on the internal surface side of the fluorescent film 84,the metal back 85 is generally provided. The functions of the metal back85 are, for example, to improve the brightness by specularly reflectingpart of light emitted from the fluorescent film, which is incident onthe internal side, to the face plate 82 side and to serves as an anodefor applying an electron beam accelerating voltage. The metal back 85can be formed by the steps of smoothing (in general, called filming) thesurface of the fluorescent film at the internal side following theformation thereof, and then depositing aluminum (Al) by vacuumdeposition or the like.

In this example, as a material for the face plate 82, PD-200(manufactured by Asahi Glass Co., Ltd.), which is an electric glass usedfor plasma display containing a small amount of alkali component, wasused as was the case of the rear plate 81.

When a support called a spacer 205 (see FIG. 1) is provided between theface plate 82 and the rear plate 81, the envelope 90 having a sufficientstrength against an atmospheric pressure can be formed so as to be usedfor a large area panel.

The support frame 86 was adhered to the rear plate 81 with a frit glass202 and was then fixed thereto by firing at a temperature of 400 to 500°C. for 10 minutes or more. In addition, the support frame 86 and theface plate 82 were bonded to each other with an In film 93, which wasused as the bonding agent, provided therebetween.

The support frame 86 and the spacer 205 were formed so that the heightof the spacer 205 was slightly higher than that of the support frame 86adhered to the rear plate 81 with the frit glass 202, and hence thethickness of the In film 93 after the bonding was determined.Accordingly, the spacer 205 also functioned as a member defining thethickness of the In film 93.

Since evolving a small amount of gas even at a high temperature andhaving a low melting point, the In film 93 was used. When a metal or analloy is used as a bonding agent, it is not necessary to use a solventand a binder. Since a material containing a solvent and a binder is notused for a bonding agent, the amount or gas evolved therefrom can bedecreased.

An underlayer 204 was provided on the support frame 86 corresponding tothe first member. By this underlayer, the adhesion at the interfacecould be enhanced. In this example, silver was used which had a goodwettability to metal In used as a bonding agent. The underlayer 204 madeof silver can be easily formed by screen printing so as to have adesired shape. As the underlayer 204 for the In film 93, a thin metalfilm made of ITO, Pt, or the like may also be used. The underlayermentioned above may also be provided by vacuum deposition.

A contact member 203 was provided on the face plate 82 corresponding tothe second member. In this example, a SiO₂ film primarily composed ofSiO₂ was used. The contact member 203 made of the SiO₂ film was formedby screen printing of an insulating printing paste primarily composed ofSiO₂. As a method for forming the contact member 203, for example, amethod of applying a sol-gel solution by spin coating or dipping or avacuum deposition method such as sputtering may also be mentioned.

Before the face plate 82 and the rear plate 81 were bonded to eachother, that is, before the sealing was performed, the In film 93 waspatterned beforehand. Referring to FIG. 16, a method for forming the Infilm 93 on the support frame 86 adhered to the rear plate 81 will bedescribed.

First, in order to further improve the wettability of molten In to theunderlayer, the support frame 86 was held in a sufficiently heatedstate. The heated state at a temperature of 100° C. or more wassufficient. The underlayer 204 made of a silver paste was a porous filmcontaining a large amount of air voids inside although having a highadhesion to glass. Hence, in this example, in order to impregnate theunderlayer 204 with the molten In, the molten In at the melting pointthereof or more was soldered to the underlayer 204 by a ultrasonicsoldering iron 215, thereby forming the In film 93. Liquid In melted ata temperature of 200° C. or more will be good enough for this step. Themetal In was supplied whenever necessary to the front end of thesoldering iron 215 by an In supply unit (not shown in the figure) sothat a position at which the In film 93 is formed is always providedwith In. In addition, in order to obtain a sufficiently large thicknessof the In film 93 as compared to that of the In film 93 after thebonding, the moving speed of the ultrasonic soldering iron 215 and thesupply amount of In were controlled. In this example, in order to formthe In film 93 after sealing to have a thickness of approximately 300μm, the film thickness of the In film 93 provided for the support frame86 was set to approximately 500 μm. The In used as the bonding agent wasprovided on the underlayer under atmospheric conditions.

After formed on the support frame 86 by the forming method shown in FIG.16, the panel was formed by a sealing method shown in FIG. 17. This stepand the subsequent steps were performed in a vacuum chamber. While apredetermined distance between the face plate 82 and the rear plate 81was maintained, the two substrates were heated under vacuum conditions.Vacuum baking was performed at a high temperature, such as 300° C. ormore, so that gases were evolved from the substrates and that when thetemperature was decreased to room temperature, the inside of the panelwas at a sufficient vacuum level. In this step, the In film 93 wasmelted and had high fluidity. In order to prevent the molten In fromrunning off, the rear plate 81 was very strictly maintained in thehorizontal position. After the vacuum baking, the temperature wasdecreased to a temperature close to the melting point of In, and bygradually decreasing the distance between the face plate 82 and the rearplate 81 so that the two plates were brought into contact with eachother, the two plates were bonded to each other, that is, the sealingwas performed. The reason the temperature was decreased to a temperatureclose to the melting point was to decrease the fluidity of the liquid Inin a molten state so as to prevent the In from running off or protrudingin bonding.

In the method for forming the In film 93 described above with referenceto FIG. 16, an oxide film was formed on the surface thereof. In thisexample, in order to decrease the variation in thickness of the In film93, the underlayer 204 was used. In addition, the structure in which theIn film was not formed at the face plate 82 side was used. Furthermore,on the substrate at the face plate 82 side, a SiO₂ film (contact member203), which was likely to be bonded to the oxide film present on thesurface of the bonding agent, was formed beforehand by screen-printingso that the In film (In film having an oxide layer on the surfacethereof) was likely to be bonded with the SiO₂ film.

After the display panel as shown in FIG. 13 was manufactured asdescribed above, a drive circuit including a scanning circuit, a controlcircuit, a modulation circuit, and a DC power source was connected tothe display panel, thereby manufacturing a flat type image displaydevice.

According to the basic properties of a surface conduction type electronemission element formed as the electron source of this example, theamount of emission electrons from the electron emission portion iscontrolled by the peak value and the width of the pulse voltage appliedbetween the element electrodes facing each other when the voltage isequal to or more than the threshold voltage, the amount of charges isalso controlled by the intermediate values of the voltage and the width,and hence gray display can be performed.

In addition, in the case in which a great number of surface conductiontype electron emission elements are disposed, when a selection line isdetermined in accordance with a scanning signal of each line, and thepulse voltage is appropriately applied to each element via theinformation signal line, a voltage can be appropriately applied to anoptional element, and as a result, each element can be turned on.

In the image display device of this example, through the X-directionwires and the Y-direction wires, predetermined voltages were applied tothe individual electron emission elements in a time-sharing manner, anda high voltage was applied to the metal back 85 through the high voltageterminal Hv; hence, a superior optional image pattern formed in a matrixcould be displayed without any pixel defects.

Example 2

In FIGS. 18 and 19, another example of the present invention is shown.FIG. 18 is a schematic cross-sectional view of a bonded portion at theperiphery of an envelope, and FIG. 19 is a schematic view of a bondingstep.

In this example, the bonding between the support frame 86 and the rearplate 81 was also performed with an In film. That is, the support framecorresponded to the first member, and both the face plate and the rearplate corresponded to the second member. Wires were provided for therear plate 81 which were used for applying a voltage. A contact member203 b was a PbO film primarily composed of PbO. This contact member wasused to improve the bondability to the bonding agent and, in addition,was also used as an insulating layer for insulating the In film used asa bonding agent from the wires. The rest of the structure was equivalentto that in Example 1. FIG. 23 shows the state in which the PbO film,which was used as the interlayer insulating film and the contact member,was provided on the rear plate corresponding to the second member so asto cover wires. FIG. 23 shows the structure of the bonded portion of theenvelope when it is viewed from the left side in FIG. 18. A plurality ofthe wires was covered with the contact member 203 b and theirregularities formed by the presence of the wires were smoothed also bythe contact member 203 b. As was the case of Example 1, the contactmember was provided all along the periphery of the envelope, and hencethe bonding of the envelope was achieved along the entire peripherythereof.

In this example, a film primarily composed of SiO₂ was used as a contactmember 203 a at the face plate side, and a film primarily composed ofPbO was used as the contact member 203 b at the rear plate side;however, the advantages can be obtained even when the combination of thefilms described above is optionally changed. In addition, the structurewas used in which the underlayer was formed on the support frame and inwhich the face plate and/or the rear plate was provided with the contactmember; however, the underlayer provided with the bonding agent may beformed on the face plate and/or the rear plate, and the contact membermay be formed on the support frame.

Furthermore, in above Examples 1 and 2, the sealing process wasperformed under vacuum conditions; however, the present invention may beeffectively applied to the case in which the envelope 90 having a vacuumspace is formed by the steps of performing sealing under atmosphericconditions, and then evacuating the inside of the panel through anexhaust hole which is separately provided in the substrate.

According to the embodiments described above, an envelope capable ofmaintaining a high vacuum lever can be manufactured at a low cost. Inaddition, when the electron emission element and the display deviceusing the same as an electron source are formed, an image display devicecan be manufactured having high electron emission properties under highvacuum and having superior display quality.

According to the present invention, a highly reliable bonding can berealized, a highly reliable airtight container can be manufactured, andin addition, a preferable image display device can be manufactured.

While the present invention has been described with reference to whatare presently considered to be the preferred embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments. On the contrary, the invention is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims. The scope of the following claims is to beaccorded the broadest interpretation so as to encompass all suchmodifications and equivalent structures and functions.

1. A method for manufacturing an image display device, comprising: afirst step of forming an underlayer on a first member; a second step ofproviding a bonding agent on the underlayer; a third step of forming acontact member, which comprises a different material from a material ofthe bonding agent and a material of the underlayer, on a second member;a step of bringing the bonding agent into contact with the contactmember and bonding the first member to the second member; and a step offorming at least one of a display element, a wire, an electrode, and afluorescent on the first member or the second member, wherein thewettability of the bonding agent to the underlayer is superior to thatof the bonding agent to a surface of the first member prior to the firststep, and the bondability of the bonding agent to the contact member issuperior to that of the bonding agent to a surface of the second memberprior to the third step.
 2. A method for manufacturing an image displaydevice, comprising the steps of: forming an underlayer which comprisessilver, gold, platinum, or an alloy thereof on a first member; providinga bonding agent which comprises indium or an indium alloy on theunderlayer; forming wires on a second member; forming an oxide film onthe wires formed on the second member; and bringing the bonding agentinto contact with the oxide film and bonding the first member to thesecond member.
 3. The method for manufacturing an image display deviceaccording to claim 1, wherein the bonding agent comprises a metal. 4.The method for manufacturing an image display device according to claim1, wherein the underlayer comprises a metal.
 5. The method formanufacturing an image display device according to claim 3, wherein theunderlayer comprises a metal which is unlikely to be oxidized ascompared to the metal for the bonding agent.
 6. The method formanufacturing an image display device according to claim 1, wherein thebonding agent comprises an oxide at a position which is to be broughtinto contact with the contact member.
 7. The method for manufacturing animage display device according to claim 2, wherein the bonding agentcomprises an oxide at a position which is to be brought into contactwith the oxide film.
 8. The method for manufacturing an image displaydevice according to claim 1, wherein the contact member comprises anoxide at a position which is to be brought into contact with the bondingagent.
 9. The method for manufacturing an image display device accordingto claim 8, wherein the oxide comprises SiO₂ or PbO.
 10. The method formanufacturing an image display device according to claim 2, wherein theoxide comprises SiO₂ or PbO.
 11. The method for manufacturing an imagedisplay device according to claim 1, wherein the second step isperformed under the conditions in which at least a surface of thebonding agent is oxidized.
 12. The method for manufacturing an imagedisplay device according to claim 2, wherein the second step isperformed under the conditions in which at least a surface of thebonding agent is oxidized.
 13. The method for manufacturing an imagedisplay device, according to claim 1, wherein one of the first memberand the second member is a substrate on which at least a part of thedisplay element, the wire, the electrode, and/or the fluorescent isformed and the other comprises a frame part of an airtight containerforming the image display device.
 14. The method for manufacturing animage display device, according to claim 2, wherein the second member isa substrate on which the wires are formed and the first member comprisesa frame part of an airtight container forming the image display device.15. The method for manufacturing an image display device according toclaim 3, wherein the metal composing the bonding agent is oxidized atleast at a position which is to be brought into contact with the contactmember.